Control of electrical energy



Aug. 10 1926.

CONTROL 0F ELECTRICAL ENERGY c. A. sPRAGUE Filed April 1, 1918 all / VEN TOR MM @ff/L7M Patented Aug. 1o, 1926.

CLARENCE A.'SPRAGUE, 0F EAST ORANGE, NEW JERSEY.

CONTROL 0F ELECTRICAL ENERGY.

Application filed April 1, 1918. Serial No. 226,127.

This invention relates to a method of and means for quantitatively controlling large amounts of energy for any desired purpose through the use of a small controlling force.

It often becomes desirable to producel .a large periodic force having a period the same as that of agiven smaller force, as for example in the reproduction of an amplified sound wave or etheric or electronic wave. To do this it becomes necessary to provide a relatively large supply of energy and to periodically transform or direct portions of this energy at the desired rate, or to bring a large force into play in such manner as to produce the desired form of energy at the desired rate. It is difficult to do this autoniatically by means of a relatively small controlling` force such as that of a sound Wave to be amplified. One of the objects of this invention is to provide a method of and means for accomplishing this in such manner as to produce much greater amplification than that ordinarily obtained. In the know methods of amplification it is often necessary to perform the process in several stages before the desired degree of amplification is obtained. By my invention a large amplification may be obtained in a single stage. No limitation is introduced by rea` son of the usual distortion in the amplifying device. Other objects of my invention will appear from the following description and appended claims.

In accordance with my invention electricity is set in motion and controlled by a device in the nature of a gatc-valve which in turn is controlled by the relatively small amounts of energy obtained from the force or wave to be amplified or reproduced. and the force exerted by the moving electricity upon the valve device, or the charge thereon, is removed or greatly reduced at intervals to permit the valve to be repeatedly reset and locked.

`My invention will be better understood by reference to the accompanying drawings in which: f

Figures 1, 2 and 3 are diagrammatic views of three different forms of electrical reproducing or amplifying systems according to my invention.

lteferrin to Fig. 1, the speech or sound to be repro uced or intensified impinges upon the'diaphragm of the transmitter 1. The current from the battery 4 in the transmitter circuit is thus varied in accordance with the sound Waves and these variations induce an alternating current of similar characteristics inthe secondary circuit'of the transformer 2, 3. The current through the secondary 3 oscillates between the condenser 5 and the grid 11 of the vacuum gate-valve device 10. A very small spark gap 9 is inserted in the circuit between the secondary 3 and the grid 11. Adjacent this spark ga is an ultra violet light source shown in tiie drawing as a mercury vapor rectifier 16, having the side branch circuit 17, which maintains the lower end of the mercury column in the tube conductive. To render the tube a positive rectifier it may be necessary to provide cooling means for the upper portion of the tube.

The purpose of this ultra-violet light source is to periodically ionize the spark gap 9. Also adjacentthe spark gap 9 is a blow-out coil 15, the purposeof which is to periodically render the spark gap 9 non-conducting. The coil 15 and the light source 16 are connected in shunt with each other and with the inductance coil 18 of the main oscillatory circuit II.

Instead of providing a continuous current whose energy is to be controlled by the energy of the speech currents. I employ an oscilating current of relatively high frequency. This current flows in the circuit II. The oscillations are induced by means of the transformer 22, 23, the primary of which is connected to a source of oscillations of the desired frequency. The source of oscillations is shown in the drawing as a quenched Spark gap circuit III containing the rectifying device 24 and the spark-gap device 25. Any other known source of oscillating currents may, however, be employed.

The circuit II may be. tuned to the frequency desired (preferably that of the source of oscillations III) by means of the variable inductance 18 and variable condenser 21. The variable impedance 19 may be placed in the circuit Il in shunt to the valve device 10, if desired, by means of switches 26 and 27.

The gate-valve device 10 consists of an evacuated container for the grid 11 and the Yheated filaments 12 and 13. The grid and filaments are similar to those employed in the vacuum tube device known as the audion, the filaments being maintained in a heated condition by means of the battery 28 in the well known manner. This gate-valve device is conducting in both directions, its conductivity depending upon electrical conduitions of the grid 11. For the purpose of this invention the vacuum of the device 10 and the other vacuum devices shown in the drawing may vary within wide limits. It may be so high that the discharge will be entirely electronic or it may, on the other hand, approach atmospheric pressure if means are provided to prevent disintegration of the heated filaments.

rThe rectifier 14 is placed in series with the blow-out coil 15 for a purpose which will later appear.

The receiving circuit 1V is shunted around the condenser 21. 1t consists of a condenser' 20, the rectifying device 8 and the telephone receiver 7.

A battery 29 of any desired voltage may be connected around the condenser 5 by means of the switch 31. The function of this battery is to place a negative charge upon the grid circuit.

A relatively high variable resistance 30 may be connected to the circuit of grid 11 by means of switch 32. 1t may be necessary to employ this resistance to permit a leakage of an excessive charge which may accumulate upon the grid 11.

The operation of the system shown in Fig.

1 is as follows: A frequency of oscillation is chosen for circuit 11 which is much greater than the frequency of the sound wave to be reproduced and is preferably, tho not necessarily, above the upper limit of audibility. The impedance of the gate-valve 10 being relatively high, the circuit 1I may not be a. very persistent oscillator. In such case the circuit 11 should receive an impulse during each period. This impulse may be in either direction but is preferably that indicated by the position of the rectifying device 2l, which will induce a current in the circuit I1 in the direct-ion of the arrow. 1f the circuit I1 is a persistent oscillator the circuit III may be adjusted to impart impulses to the circuit 11 at less frequent` intervals and at such times as not to oppose the current in the circuit II.

When the current in circuit II is in the direction shown by the arrow, the potential drop across the co-il 18 will tend to produce a current through the lamp 16 and the blowout coil 15. Assuming for convenience that current in the circuits flows from negative to positive, this being the direction in which an electronic discharge appears to take place across an evacuated space or gap in the circuit, such as the gap within the space discharge device 10, current will .flow from the left. end of coil 18 to the rectifier 14 and blow-out coil 15 back to t-he circuit II. No current will fioW through the lamp 16 which is conduct-ive only in the reverse direction. The blow-out coil 15 will instantly render kthe gap 9 non-conducting.

Then the current in the circuit II is in the opposite direction to that indicated by the arrow, the drop in potential across the coil 18 will cause a current to fiow through the lamp 16 but can not produce a current through the blow-out coil 15 because of the rectifier 14.

It is seen therefore that the gap is rendered alternately conducting and non-conducting by the current in the main circuit H.

r1`he impedance of the valve device 10 varies with the charge upon the grid 11. The grid is preferably maintained negatively charged by means of battery 29. During operation of transmitter 1, the negative charge upon the grid 11 will rise and fall in accordance with the variations in the speech waves.

Assuming that the current in the main circuit 11 is at zero value, and about to begin to flow in the direction opposite to that indicated by the arrow, the gap 9 is non-conducting and there is a certain negative charge upon the grid 11. As soon as the current begins to flow lamp 16 will be light.- cd thus rendering the spark gap 9 conducting. There follows an immediate readjustment of the charge upon the grid 11. Since there is always a. tendency for the charge on the grid to be varied by increasing or decreasing of the current flowing through the valve and by changes in the charge upon the other elements Within the evacuated space, as the current increases from zero to its maX- imum value in the circuit I1, the negative charge upon the grid tends to decrease and will do so unless the electro-motive force in coil 3 happens to be sufiiciently great and in the right direction to prevent. As the current falls to zero value again, its effect upon the grid charge likewise falls to zero. This rise and fall of current in the circuit Il has had no effect upon the receiver 7, the current being in such direction that it could not pass through the rectifier 8.

The succeeding half wave of currentin the circuit I1 is the effective or working portion of the current. It is in such direction as to pass through the rectifier 8 and operate the receive-r 7. As the current begins to rise the charge upon the grid is substantially the same as though the grid were removed from the valve 10. At this instant the blow-out coil becomes operative and the charge upon the grid is therefore trapped and remains so until the current in the main circuit again reverses. This will be for a very brief time as Compared. with the period of the voice currents.

The relatively small amounts of energy which are present in the grid circuit are thus enabled to control the large amount of energy of the current of the main circuit II.

Assuming, for example, that the frequency of the sound wave is 500 and that of the oscillating currents 25,000, there will be fifty readjustments of the charge upon the grid during the period of a sound Wave. The effective half Waves of the current in the circuit II are therefore varied in amplitude in accordance with the sound waves. T he current through the receiver 7 will cause the reproduction of the original' sound Waves but which greatly increased volume.

The function of the condenser 20 is to partly smooth out the high frequency variations in the rectified current without affecting the characteristic of the amplitude variations.

The rectifier 33 may be inserted in shunt to the valve device 10 if desired. The impedance of this rectifier may be very small compared with that of the device 10, so

` that the effect will be to substantially shortcircuit the valve 10 during the non-effective parts of the main current wave.

If the valve device 33 is employed an ordinary audion type of valve may be substituted for the valve 10. That is, a plate may be substituted for the filament 12.

If the vacuum Within the device 10 is not so high that the discharge is entirely electronic, the effect of the space current upon the negative charge of the grid 11 may not be so great, as ionization will of course take place and both positive and negative ions will be present, but, in general, there will be some tendency for the grid chargel to vary Whenever the space current conditions in the device 10 change, whatever the nature of the space current.

The principle of operation of the system shown in Fig.2 is, in the main, the same as that of Fig. l. In place of the microphone circuit I of Fig. 1 a receiving antenna is shown. This is inductively connected to the grid circuit which extends from the 'ground 57 to the grid 35. A battery 52 may be inserted in this circuit by opening the switch 53 and closing the switch l. coil of high resistance such as that shown at 30, Fig. 1, may be connected between the grid and ground if desired.

The spark-gap 49 is inclosed in a vessel 50 which. may contain air, or other gas, at any desired pressure. The blow-out coil 47 causes the ionized gasto be brought in contact with tube 51, which is of non-conducting material and through which aA cooling fluid is circulated. The ionized gas is thus deionized.

Ionization ofthe spark-gap 49 ispoduccd by. means of the ultra-violet light om the spark-gap 45. This light is foissed upon 474, 75, 77, 92 and 93. Inductances 91 an the gap 49 by the mirror 46. Thevessel 50 must be of a material which is transparent to ultra-violet light or must have a Window 'of such material.'

In this modification the blow-out coil and light source are in shunt to the condenser 42 and are in series respectively with the rectifiers 43 and 44.

The gate valve device 34 is in this figure represented as a mercury vaportu-be having mercury electrodes 37 and 38 and 'side-branch circuits 39 and 40. The lower fiattened Wall of the midportion of the tube is in contact with a cooling fluid in the receptacle 36. The grid 35 consists of one or more semicircular grid elements having the lower straight side parallel to the flattened lower Wall of the mid portion of the tube 34. y The electronic or arc stream through the tube 34;V will not only be impeded by passage through the grid 35 but will be deflected downward thereby and into contact with more or less of the cgol tube surfa'e.

The receiving circuit IV is the same as that of Fig. 1 except that it is connected tothe circuit II through a transformer 55.

A variable inductance coil 4l is included in the circuit II.

In Fig. 3 is shown a modification in which a valve tube 67 of the audion type .is substituted for the tube 10 of Fig. 1 and in which the current in the main circuit II periodically falls to zero but does not reverse.

In place of the spark gap 9 of Fig. 1 with the associated blow-out coil and source of ultra-violet light a `double audion-type tube is used. rlhis consists of filaments 6l and 64, plates 62 and 63 and grid 65. The grid 89 of the valve 67 may be connected to elements 61 and 62 of tube 60. Elements 63 and 64 of this tube are connected to the plate of the valve 67 through the antenna. transformer.

The grid 65 is connected to the plate of the valve 66 and also by conductor 94 to the potentiometer 96 receiving current from battery 95.

' The double tube 60 should be small, of low impedance when the charge on the grid such that its impedance efi'egt is a minlmum, and ofvery small capacity.

66 is a second tube ofthe audion type. the function of which is to periodically reduce the current strength in the circuit II to zero value. This tube 66 is normally7 in series with the tube 67 in the circuit II. It will be understood that the function of the tube 67 is to change the impedance of the circuit II in accordance with the voice currents of the antenna circuit.

The circuit II is a divided -circuit and inductance 81 and condensers 69, 70, 76 and 90 may be cut into or out of circuit as de,- sired by means of switches 82, 71, 72,73,

means of switch 88. The latter connection is preferred.

The operation of this system is similar to that of F ig. 1 and may be described as follows. Initially, current from battery 8O flowing towards coils 81 and 91 divides, part returning to the battery throu h the coil 81, tube 86, tube 67 and trans ormer 79. The other part of the current flows through coil 91, the branches containing condenser 76 and inductance 84 and condenser 69, respectively, the condenser to the grid of the tube 66. This part of the current flows only momentarily, as it is merely condenser charging current. By a proper adjustment of the variable inductances and capacities, a reaction may be set up by which the current iiowing into the grid of the tube 66, completely stops the iow of current through this tube, an oscillation in the circuit 84, 69, 76 immediately following whereby the charge is withdrawn from the grid and the current again flows through the tube 66. Thus oscillations are set up and maintained.

The function of the double audion 60 is to render the receiving circuit 89, 60, 88 conducting at the instant that the current through the tube 66 falls to zero. By conducting i I mean conducting to the same degree as tho the double grid 65 were removed from the double audion 60. To establish this condition it is necessary to bring the twin grids 65 to a certain low potential which must be determined by trial. The grid 65 is covered with a thin layer of insulation to prevent leakage of current from the receiving circuit. If this grid were charged positively there would be an accumulation of negative charge upon the outside of the insulation. Thls condenser effect may be diminished or overcome by making the grid slightly negative. This may be done by adjustment of the potentiometer during operation of the system until the minimum effect is obtained in the telephone receiver.

When the current in the circuit II begins to flow again, the charge upon the grid 65 immediately changes to a value which will render the tube 60 non-conducting, thus trapping upon the grid 89 any charge which happens to be there at the instant. Incldentally, the increase in negative charge thus produced upon the grids 65 will induce a charge upon the grid 89, owing to the unavoidable capacity effect. between 'the grid 65 and plate 63. However, any'eifect which is thus produced upon the current through the transformer 79 will be in the direction of increasing the amplifying ower of the system since an increase of c arge upon grid 89 causes an increase in char e upon grid 65. This reaction may even e suiiicient to stop the iow of current through the valve 67 whereby this current will be interrupted at intervals between the interruptions produced by thevalve 66- If this effect is found to be undesirable it may be eliminated by decreasing the size of the plate 62 or by introducing resistance in the circuit of the grids 65. No such effect will occur if the tube 67 is short-circuited and the switches 68 and 83 are thrown to connect the grid of the tube 66 with the plate 62.

It will be understood, of course, that the interru tions of the current in the circuit II caused by the tube 66 must be of very high frequency compared with the frequency of th-e current in the receiving circuit. The surges of current through the transformer 7 9 will vary in amplitude according to the form of the current in the receiving circuit and the telephone receiver will reproduce the original sound with greatly increased intensity.

There are many combinations both of elements and method steps which I have described above which are features of my invention and which are pointed out in the claims. These combinations will without doubt come lto be of more general application than for use in reproducing systems, to which, therefore, my invention in these respects is not limited.

I claim:

1. The combination with an electric discharge device having a cathode, an anode and an impedance control element, of a source of alternating current connected to said anode and said cathode, a source of variable potential connected to said impedance control element, and means associated with said anode and said cathode for causing each of them to emit electrons continuously.

2. The combination with an electric discharge device having thermionically active electrodes and an impedance element to control current flowing therebetween, of an alternating current source connected to said electrodes, a source of variable potential, means conductively connecting said source of variable potential to said impedance control element, and means controlled by the current between said electrodes to periodically vary the conductivity of said connecting means.

3. The method of controlling the How of current along a current path which comprises alternately increasing and decreasing the current is at or near its mimmum value,

and automatically preventing the variation of saidcharge by an increase of current.

4. The method of controlling the flow of current' alon a current path which comrises periodically reducing the current ow, var ing the condition of impedance to current ow only while the current is small, and automatically maintainin said condition substantially uniform whi e the current is increasing.

5. The method of controllin current through an electric the iow of iary control element, the latter controlled by a source of variable potential, which method comprises periodicall varying the current between sald main eectrodes at a rate different from the rate of variation of the potential of said source, ermitting said source of variable potentiall to vary the charge upon said control element, while the reaction upon said control element by the main current is at or near its mimmum value, and automatically removing said control element from the influence of said source of variable potential at other times.

6. The combination with an oscillation circuit, of a valve in said circuit, a source of variable potential for controlling the conductivity of said valve, a circuit connectin said source and said valve, and a secon valve in series in said connecting circuit controlled by said oscillation circuit.

7 An electric relay comprising an oscillation circuit, a valve in said circuit, a sound vcontrolled circuit controlling said valve, and

a valve in said last mentioned circuit controlled by said oscillation circuit and in turn controlling said first mentioned valve 8. The combination with space discharge electrodes, of ionizing means adjacent said electrodes, deionizing means adjacent said electrodes for quickly removing substantially all ionized gas from the space between said electrodes to render said space substantially non-conductive, and means rendering said ionizing means and said deionizing means alternately operative.v

9. The combination with an electron emitting anode, of an electron-emitting cathode,

means for causing current iow from one of said electrodes to the other, and means inductively related to the current path between said electrodes for varyingV the current iow.

10. The combination with separated circuit terminals, of means for periodically producing a discharge across thegap between the terminals, auxiliary means associated with said terminals for controlling the discharge, a source of current, connections rom said source to said auxiliarycausin ischarge -device having mam electrodes and an auxllmeans, andv means for periodically interrupting said connections at the saineratel as the discharge across the ap.

11. Tle combination wit an electricity conductin device, of means for periodically t e flow of current therethrou h, contro ling means adjacent said device or affecting the current flow therethrough, a.

source of electricity for impressing a varying potential upon said controlling means, and means for periodically disconnecting said source from said controlling means at the same rate at which current flows through said device.

12. A divided control circuit having a rectifier in each branch, and a resistance element whose resistanceis increased and decreased by the current in the two branches respectively.

13. The combination with an electric discharge device having incandescentlamenvtary electrodes and a grid therebetweemof a source of alternating current connected to said electrodes, and a source of variable potential connected to said grid, said electrode serving alternately -as cathode and anode.

14. The combination with a main circuit, of means for contrellin the discharge across a gap in said main clrcuit, a source of controlling current, circuit connections between said means and said source of controlling current, anda variable impedance in said circuit connections, said variable impedance being under the control of said main circuit.

15. The combination with a main circuit, of a discharge device therein, an impedance control element for said discharge device, means causing the current throu h said discharge device to periodically all to zero value, and circuit connections between said main circuit and said impedance control element for varying the charge on said element at the rate at which said main current falls to zero value.

16. The combination with a main circuit', of a discharge device therein, an impedance control element for said discharge device, means causing the current through said discharge device to periodically fall to zero value, and a valve controlling said impedance control element, said valve being under the control of said main circuit.

17. The combination with an electric circuit, of a bilaterally conducting electric discharge device and a unilaterally conducting discharge device in parallel in said circuit, and means for impressing alternating current u on said circuit.

18. 'Ihe combination with a normally nonconducting `discharge gap, of ionizing means adjacent said gap, deionizing means adjacent said gap, and means rendering said ionizing and said dcionizing means alternately operative.

19. A thermionic discharge device comprising main electrodes and an impedance control element, a circuit connecting said main electrodes, circuit controlling means 1n said circuit, means associated With said main electrode circuit for causing the potential of one of said main electrodes to be alternately greater and less than that of the other main electrode and for causing successive reversals of current through said circuit controlling means.

20. A discharge device comprising main electrodes and an impedance control element, a circuit connecting said main electrodes, a circuit controlling means in said circuit, means associated with -said main electrode circuit for causing the potential of one of said main electrodes to be alternately greater and less than that of the other main electrode and for causing successive reversals of current through said circuit controlling means.

2l. The combination With an .electrical discharge device comprising discharge electrodes and an impedance control element, of means for periodically and automatically connecting said element to a source of unidirectional electromotive force.

22. The combination With an electrical discharge device comprising discharge elec.- trodes and an impedance control element, of means comprising a space discharge gap for periodically and automatically connecting said element to a source of variable potential,

23. The method of controlling the How of current through an electric discharge device having main electrodes, a source of cur-y rent for supplying said main electrodes and an auxiliary control element, the latter controlled by a source of variable potential, Which method comprises periodically vary- 4 ing the current between said main electrodes by var ing the current from said source externally of said discharge device, permitting said source of variable potential to vary the charge upon said control ele- `ment, While the reaction upon said control element by energy from said source of cur' rent is at or near its minimum value, and automatically removing said control element from the influence ozt said source of variable potential at other times.

24. The combination with an electrical circuit, of a valve in said circuit, a source of variable potential for controlling the conductivity of said valve, a circuit connecting said source and said'valve, a second valvev in said connecting circuit controlled by said first mentioned circuit, and a second source of variable potential for controlling the conductivity of said second valve.

25. A space discharge device, a source of alternating potential, circuit connections for serially relating said space discharging device and said source, and a uri-laterally conductive device, the impedance oi' which is small compared with that ot said space discharge device` in effective shunt to said device, whereby said uni-laterally conductive device transmits the greater poit'on of the current from said-source during one half ot each cycle.

26. The combination with a vulve comprising main electrodes and an impedance control element, of an output circuit comprising said main electrodes, a second valve controlling said iirst valve and having main electrodes and an impedance control element, means for setting up periodically varying current in said output circuit, and means for ,feeding back a portion of the variable energy in the output circuit to said second impedance control element to periodically render said second valve incapable of passing current.

2?. The combination With an electric valve comprising main electrodes and an impedance control element, of an output circuit for said valve comprising said main electrodes, a source of variable potential, a current path from said source to said impedance control element, and means associated with said current path to vary the instantaneous value of the control energy of the impedance control element by an amount and in a direction which tend to compensate for the reaction of said valve upon said impedance control element.

28. The combination with an electric valve comprising main electrodes and an impedance control element, of an output -circuit comprising said main electrodes, a source of variable negative potential, a current path from said source to said impedance control element for impressing a variable negative charge upon said element, and means associated With said current path to vary the instantaneous value of the control energy of the impedance control element by an amount and in a direction which tend to compensate for the reaction of said valve upon said impedance control element.

29. The method of amplifying variable currents by means of an electric discharge valve having main electrodes and an output circuit containing said main electrodes, means for controlling the impedance of said space discharge valve and a source of variablc potential to be amplified, Which method comprises varying the instantaneous value of the control energy effective to vary the impedance of said space discharge valvel and derived from said source by an amount and in a direction to compensate for the eiiect of the 'reaction of said valve upon the impedance controlling means.

30. The combination With three current paths in parallel relation, of a space'discharge device in one of said paths, means nasV in another of said paths for decreasing the impedance of said space discharge device, and means in the third of said paths for increasing the impedance of said space discharge device.

3l. The combination with three current paths in parallel relation, of a space discharge device in one of said paths, means in another of said paths Jfor decreasing the impedance of said space discharge device, and means in the third of said paths for increasing the impedance of said space discharge device, the paths in which said impedance control means are located being unilaterally conducting in opposite directions with respect to each other.

CLARENCE A. SPRGUE. 

